﻿    <p>
      The <em>IfcAxis2Placement3D</em> provides location and orientations to
      place items in a three-dimensional space. The attribute
      <em>Axis</em> defines the Z direction, <em>RefDirection</em>
      the X direction. The Y direction is derived.
    </p>
    <blockquote class="note">
      NOTE&nbsp; The <em>RefDirection</em> does not have to be
      orthogonal to <em>Axis</em>.
    </blockquote>
    <p>
      If the attribute values for <em>Axis</em> and
      <em>RefDirection</em> are not given, the placement defaults to
      P[1] (x-axis) as [1.,0.,0.], P[2] (y-axis) as [0.,1.,0.] and
      P[3] (z-axis) as [0.,0.,1.].
    </p>
    <table>
      <tr>
        <td>
          <img src="../../../figures/ifcaxis2placement3d-layout1.gif" alt=
          "axis2 placement 2D" border="0" height="300" width="400">
        </td>
        <td style="vertical-align:bottom">
          <blockquote class="note">
            Figure 2 illustrates the definition of the
            <em>IfcAxis2Placement3D</em> within the three-dimensional
            coordinate system.
          </blockquote>
        </td>
      </tr>
      <tr>
        <td>
          <p class="figure">Figure 2 &mdash; Axis2 placement 3D</p>
        </td>
        <td>
          &nbsp;
        </td>
      </tr>
    </table>
    <blockquote class="extDef">
      NOTE&nbsp; Definition according to ISO/CD 10303-42:1992<br>
      The location and orientation in three dimensional space of
      three mutually perpendicular axes. An axis2_placement_3D is
      defined in terms of a point (inherited from placement
      supertype) and two (ideally orthogonal) axes. It can be used
      to locate and orientate a non axi-symmetric object in space
      and to define a placement coordinate system. The entity
      includes a point which forms the origin of the placement
      coordinate system. Two direction vectors are required to
      complete the definition of the placement coordinate system.
      The axis is the placement Z axis direction and the
      ref_direction is an approximation to the placement X axis
      direction.
    </blockquote>
    <blockquote class="note">
      NOTE&nbsp; Entity adapted from
      <strong>axis2_placement_3d</strong> defined in ISO10303-42.
    </blockquote>
    <blockquote class="history">
      HISTORY&nbsp; New entity in IFC1.5.
    </blockquote>